He was a Research Assistant at Stanford and EPFL, and has worked for Siemens and AT&T Bell Laboratories. In 1986, he joined Columbia University in New York, where he was last an Associate Professor of Electrical Engineering and co-director of the Image and Advanced Television Laboratory. In 1993, he joined the University of California at Berkeley, where he was a Professor in the Department of Electrical Engineering and Computer Sciences until 1997, and held an Adjunct Professor position from 1997 to 2004. Since 1995, he is a Professor of Communication Systems at EPF Lausanne, Switzerland, where he chaired the Communications Systems Division (1996/97), and heads the Audiovisual Communications Laboratory. From 2001 to 2004 he directed the National Competence Center in Research on mobile information and communication systems. He is also a Vice-President for International Affairs at EPFL since October 2004, and since March 2011 has been the Dean of the School of Computer and Communication Sciences. He became the leader of the Swiss National Science Foundation in January 2013.

He is a fellow of the IEEE, a member of SIAM, and was the Area Editor for Speech, Image, Video, and Signal Processing of the IEEE Transactions on Communications. He is also on the editorial boards of Annals of Telecommunications, Applied and Computational Harmonic Analysis and The Journal of Fourier Analysis and Application.